That's a good suggestion it is an older computer and I have never changed the
CMOS battery.
Batteries *usually* last 3-5 years, sometimes even longer. Normally
one doesn't change the battery until it shows symptoms of failing, and
those symptoms are normally that the clock loses time while the
computer is powered off.
Unlike umwhat, I don't see anything in what you describe that sounds
to me like it's likely that the battery is your problem. On the other
hand, if you want to try changing it, it's quick, easy, and
inexpensive, and can't hurt. Just don't get your hopes too high that
this will fix it.
When you say you "reloaded XP and the problem returned," did the
problem return immediately after reinstallation of Windows, or after
some period of time? How long? What else did you do during that time?